Combined cryogenic and mechanical pump for NET torus exhaust

This novel pumping concept consists of a 20 K stage to increase gas density followed by a mechanical pump operating at the same temperature. Advantages of the concept include order-of-magnitude reductions in size, weight, stored energy, eddy-current rotor heating, and sudden venting thrust when compared to a conventional turbomolecular pump scaled-up to perform the same duty. The device offers extremely low tritium inventory and near steady-state operation. Critical design and development issues include minimizing backstreaming in the mechanical portion of the pump, and eddy-current heating of the rotor.